Chronic neurologic Lyme disease has emerged as the major health care issue concerning B. burgdorferi infection, the most rapidly growing vector borne infection in the United States. Encephalopathy is the core syndrome of chronic neurologic Lyme disease. The primary goal of this project is to characterize Lyme encephalopathy. Chronic Lyme patients (n=100) will be assessed on neurobehavioral measures, as compared to controls drawn from the community (n=100) and CSF measures, as compared to an Other Neurologic Disease (OND) group (n=50). We will test specific hypotheses related to the major clinical features and pathogenesis of chronic neurologic Lyme disease. A longitudinal design over an 18 month period will allow the course and key risk factors of Lyme encephalopathy to be defined. Specific Aim 1. To define the neurobehavioral and psychological sequelae of chronic Lyme disease Specific Aim 2. To determine the pathogenesis for neurobehavioral deficits in chronic Lyme disease Specific Aim 3. To identify the clinical and laboratory factors which predict health outcome in chronic Lyme disease